The media report said one of the crew disengaged the autopilot. Depending on the severity of the turbulence it is quite possible the autopilot could not cope and in that case it disengages without pilot action. Even if one of the pilots immediately attempted to re-engage the AP, any manually applied control wheel pressures (which could occur in turbulence) will prevent the AP from engaging. If that happens in IMC then recovery success (or otherwise) is entirely dependant on the instrument flying ability of the pilot flying. That, as they say, is another story altogether...